1. Field of the Invention
The present invention relates to the processing of substrates such as semiconductor wafers. More particularly, the present invention relates to apparatus that heat a substrate, especially those that heat a substrate while the substrate is being processed.
2. Description of the Related Art
In general, semiconductor devices, liquid crystal displays, optical discs and the like are manufactured by subjecting a substrate to several processes such as spin-coating, exposure, deposition, and etching processes. The substrates almost always require heat treatment in the course of their processing. Thus, equipment for manufacturing such products typically includes several apparatus for carrying out the various processes on the substrates from which the products are made. And, each apparatus has a process chamber in which an atmosphere unique to the process is created.
Specifically, a vacuum is maintained in the process chamber while a substrate is processed and heated within the process chamber. In this respect, the substrate is sometimes heated by conduction by directly heating a support, such as chuck or susceptor, on which the substrate rests within the chamber. Alternatively, the substrate is sometimes heated using radiant heat. In this case, the walls of the process chamber that form the upper or both the upper and lower portions of the chamber are formed of quartz, and radiant heat is generated by lamps fixed in place outside the quartz wall(s) of the process chamber.
The most important aim in heating a substrate during processing is to heat the substrate uniformly. For example, a substrate is often processed using a gas that reacts with the substrate to form a desired pattern on the substrate. The desired pattern will not be formed precisely on the substrate if the temperature of the substrate varies across the substrate while the gas is being supplied to the substrate. In particular, the process will generate local defects on the substrate in the case in which the temperature of the substrate varies across the surface thereof during processing. These defects are exacerbated by the processes that are subsequently performed on the substrate. Ultimately, the defects bring about a failure in one of these subsequent processes or result in the production of a defective end product.
In addition, much of the heat radiating from the heater does not propagate to the substrate or does not propagate to all regions of the substrate directly. Thus, it takes a relatively long amount of time to heat the substrate to the desired temperature.